HELP SYS_INPUT_WAITING                             Revised John Gibson Dec 86

    sys_input_waiting(<device>) -> <integer or false>;

For an 'interactive'-type device (i.e. a terminal, Unix pipe or VMS mailbox),
this procedure returns an integer count of the number of input characters
currently available to be read on the given device, or <false> if none are
available (and a read on the device would hang up waiting for input).
For example

    sys_input_waiting(popdevraw) -> <integer>

if there is input waiting (for instance) for VED via *RAWCHARIN or
*VEDINASCII.

    For all other kinds of input device (which can't hang up on a read), it
just returns the number of characters currently in POPLOG's input buffer for
the device (which could be 0).


See also
REF *SYSIO       - for further details of I/O procedures
HELP *POPDEVIN   - returns the device for the standard input channel
HELP *POPDEVRAW  - returns the device for 'raw' terminal input/output
HELP *VEDINASCII - the character repeater used by VED
HELP *SYSTRMDEV  - tests whether a device record refers to a terminal
HELP *SYSREAD    - reads from a specified device
